1. Field of the Invention
This invention relates to a process for the remediation of plastic waste, and more specifically, this invention relates to a process for the remediation of plastic waste, such as polyethylene and polystyrene, by converting the plastic waste to carbonaceous materials using a single step thermal decomposition process.
2. Background of the Invention
Polyethylene-based automobile parts, food packaging materials, toys, and milk bottles, as well as polystyrene-based plates, cups and packaging materials comprise much of the energy and environmental burdens associated with plastic. The United States alone consumes approximately 100 billion plastic grocery bags every year. Given that a single grocery bag requires approximately 0.48 mega joules of energy to be produced (the equivalent of the amount of energy consumed by the average passenger car traveling ⅛ of a Kilometer), the production of 100 billion plastic grocery bags equals 7.75 billion miles of automobile travel, which at 30 miles per gallon average efficiency, equals 258 million gallons of gasoline.
Various methods are used to dispose of solid waste material, such as recycling and the use of landfills. Recycling is strongly encouraged by many communities, but only a small amount of the total solid waste is actually recycled. Using landfills to store plastic waste is not an effective solution as plastics are not biodegradable.
While specific recycling facilities for plastic waste exist across the globe, the success of these facilities and the technology they utilize is limited as burning of plastic releases toxic fumes into the atmosphere. Also, mixing chemically different polymers will not yield homogenous materials to make new products from the recycled waste. Current processes for the sorting of similar types of plastic waste are labor intensive and thus not cost effective.
Ideally, the recycling of plastic waste would result in the formation of usable carbonaceous product. Carbon black is one of the largest commodities of carbonaceous product with millions of tons being produced each year. Carbon black, commonly referred to as “soot”, is produced commercially by the partial combustion of petroleum. Carbon powder can take a number of forms from the most common form being amorphous graphite, some spherical particles, irregular shaped graphite, and fullerenes. There are different grades of carbon black (based on size) available. Applications for the use of carbon black tend to be for lubrication, tire and paint coloring, food coloring, and abrasives. The recent increases in oil prices have lead to increases in the price of carbon black.
Carbon nanotubes can be made by a variety of methods including laser ablation and electric arc discharge, but chemical (and plasma) vapor deposition is the method used to produce commercial qualities. On average, the cost of producing nanotubes is high, with a small number of manufacturers present in the market of producing such nanotubes. There is a lot of research on applications of the use of nanotubes. These applications vary from hydrogen storage, to composites, to semiconductors, but no specific application has seemed to reach popular commercial use, as noted by the low production and high pricing of nanotubes.
Accordingly, a need exists in the art for a method of recycling the massive amount of plastic waste that is produced. The method would convert the plastic waste into a carbonaceous byproduct that is economically advantageous, useful to manufacturers, and not harmful to the environment. The method would also require less energy than typical recycling methods.